The flight of a golf ball hit by a golf club may be explained in terms of the physical laws of angular momentum. At the point of impact between the golf club with the golf ball, the golf swing is a circular motion system consisting of a greater circle whose radius, at the time of impact, consists of the arm of the golfer extended by the golf club shaft to the head of the golf club. The direction of the angular momentum at the point of impact is perpendicular to the radius of the greater circle (reference Olenick, Apostol, Goodstein, The Mechanical Universe Introduction to Mechanics and Heat, Cambridge University Press, P. 443). The center of this greater circle is approximately at the base of the golfer's neck. It is a requirement that the center of this greater circle remain anchored at a single point in space in order to consistently transfer the optimal angular momentum of the club to the ball at impact. If the golf club is always on the optimal swing plane determined by the target, the ball, and the center of the swing circle, and the swing center remains stationary in space, the ball will be struck automatically as centrifugal force causes the golfer's wrists to unhinge and throw the clubhead out, maximizing its radius at impact. Therefore, we always want to create the same "best" circle for both direction and distance. Stated even more simply, the direction which the golf ball travels is directly related to the plane of the swing.
To produce the optimal velocity toward the target for every swing, the plane of the angular momentum system must act along a line through the ball and toward the target; thus the advice to "follow through". In general, the advice to "keep your head down and follow through" is really, in scientific terms, advice to keep the center of the circle of angular momentum constant and have the swing operate along the line from the ball to the target in order to impart the maximum angular momentum in the desired direction of the shot.
The second significant consideration is the distance the golf ball travels and that is determined by the velocity of the ball immediately after impact by the golf club. Since the weight of the golf ball is fixed and the weight of the golf club is fixed, the velocity of the ball is determined by the velocity of the club head at impact. Therefore, in order to increase distance, the golfer must increase club head speed along the target line at impact with the golf ball.
Therefore, the correct positioning of the swing plane along the target line is essential in order to be able to efficiently transfer the angular momentum from the swing to the ball to get the maximum performance, i.e., the desired direction and distance.
Heretofore, feedback about the position of the golfer's swing plane has been generally available to the golfer only after the golf shot or swing has been completed. By watching the flight of the ball on the driving range, the golfer is trying to relate the feel of the swing to the swing plane that creates the flight characteristics of direction and distance. Examination of the line of the divot is also an after-the-fact attempt to determine the swing plane and relate the after-the-shot feedback to how the swing "felt" while being executed. In order to improve, the golfer must known what were the critical elements of the swing and "remember" how they felt. Thus, up to now, the important steps in teaching golf have been to first impart information about what is important in the swing; then to coach the golfer in how that information translates into the proper feel during the swing; and finally to examine the results after the swing. There has been no way, however, to actually receive feedback about the swing while it is in progress. The golfer could only examine the results of the swing (e.g., distance, direction) and from that "after-the-swing-is-completed" information attempt to make the changes necessary for improvement.
Various patents have issued over the years on training devices designed to improve a golfer's swing. Many of the patents specifically relate to training devices which incorporate various types of light beams to assist in following the motion of the swing. Examples of various patents for these devices include U.S. Pat. Nos: 4,693,479 to McGwire; 2,080,608 to Hannaford; 2,158,211 to Aitken; 3,070,373 to Mathews et al.; 4,456,257 to Perkins; 2,787,470 to Barrus et al.; and 3,820,795 to Taylor.
The McGwire patent (U.S. Pat. No. 4,693,479) discloses a self-contained, detachable device for attachment to golf clubs to provide a visual indication of the position of the club during the swing. The device includes a light bulb attached to one end of a golf club, in an attempt to provide a beam of light extending outwardly away from the grip end of the club, so that the light beam is generated along the same common longitudinal axis as the golf club shaft. The light beam is produced by an incandescent bulb and continuously disperses as the distance from the end of the golf club to the ground increases.
The Hannaford patent (U.S. Pat. No. 2,080,608) discloses a practice stick which is weighted to have the feel of a golf club and which projects from the downward end thereof an incandescent light beam. The light beam which is produced is a transverse, elongated image on the plane surface.
In Aitken (U.S. Pat. No. 2,158,211), a light source is provided for lighting the top of the head of the club and in Taylor (U.S. Pat. No. 3,820,795) a device is disclosed which may be attached to the golf club shaft and which directs a light beam upwardly toward the golfer.
In the Perkins et al. and Mathews et al. patents (U.S. Pat. Nos. 4,456,257 and 3,073,373) additional devices are disclosed which project light beams downward along the golf club shaft to the ground. In addition, in Perkins a light beam may also be projected upwardly from the grip end by means of a fiber optics line within the golf club.
While each of these devices contains a light source for projecting light from one or both ends of the golf club, none of the patents discloses a structure which provides a definite and very distinct collimated light beam. The various incandescent light sources or fiber optic light transmission material disclosed in the patents will project a beam of light from the golf club onto a surface, but the light beam disperses as the distance from the light source to the surface increases, particularly at the top of the backswing. It is not possible, therefore, to get a continuous, distinct point light beam. Such a beam is not possible with the lens system or the fiber optic system presently taught by these various patents.
These prior golf training aids project a light beam onto the desired surface to disclose the plane of the golfer's swing. However, none of the prior devices utilizes a light source which provides a collimated light beam that does not vary in size or disperse with distance from the light source. In making sure that the golfer's swing plane is directly on target with the golf ball, it is not sufficient to have a broadly dispersed light beam. The light beam should be as concentrated as possible and the same width for the entire swing and, moreover, should not need to be readjusted for the height of each person who might use the device.